Heneik kelstad



(No Model.) V

H. KELSTAD.

TAP.

Patented 001;. 18, 1888.

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UNITED STATES PATENT OFFICE.

HENRIK KELSTAD, OF MINNEAPOLIS, MINNESOTA.

TA P.

SPECIFICATIN forming part of Letters Patent No. 391,161, dated October 16, 1888.

Application filed June 29, 1888. Serial No. 278,516. (No model.)

To all whom it may concern:

Be it known that I, HENRIK KELsTAD, of Minneapolis, county of Hennepin, and State of Minnesota, have invented certain new and useful Improvements in Taps, of which the following is a specification.

My invention relates toimprovements in an implement for cutting threads in an aperture; and it consists, generally, in the combination and arrangement hereinafter described, and particularly pointed out in the claim.

In the drawings which form a part of this specication, Figure lis a side elevation of my improved tap. Fig. 2 is a longitudinal section. Fig. 3 is a horizontal section.

In the drawings, 2 represents the body or shank of the tap. The lower extremity is provided with threads 3, and the upper extremity is furnished with asuitable socket, 4, by which the device is turned. The shank 2 is preferably split or divided into two parts, in order that the threaded portion may be thrown outward or spread and cause thecutting portion of the threads to describe a greater or less diameter, as the case may require. A setscrew, 5, may be arranged to pass through one halfof the shank 2,in which it is properly screw threaded. The extremity of this set-screw bears against the opposite half of the shank. By turning this set screw in one direction the two halves of the shank are forced apart, thus increasing the diameter or' circle described by the cuttingedges of the tap. By turning the set-screw 5 in the opposite direction the pressure between the two halves is released and the spring in the material forming the socket 4, by which the two halves are connected, will be sufficient to cause the halves to be forced back to the original position.

rIhe threaded portion 3 of the tap may be provided with the relief-notches 6 upon two sides, in order to facilitate the working of the device.

The operation of the device is as follows: Ablank is provided which is sawed or cut through the center lengthwise, and is screwthreaded at the end to give the proper pitch and diameter of thread required. The socket 4 is preferably so formed that the tension of the upper portion of the said socket, which connects the two halves closely together, causes them t0 assume the form of an ordinary straight tap. The aperture in which the thread is to be cut will be of a size ordiameter to receive the tap when closed. The threaded portion will be inserted into the aperture to the depth required for the thread. The set-screw 5 will then be turned to force apart the two halves of the tap. The tap will now be revolved by a suitable handle in the socket 4 in a direction to cut the thread outward toward the surface. When this opera` tion has been carried on sufficiently to finish the first cut, the set-screw 5 may be again turned and the two parts of the tap forced farther apart. The tap is again revolved and another cut made in the aperture, increasing the depth' of the thread already started. This operation is kept up until the full depth of the thread has been cut.

A certain amount of spring in the material of which the tap is made is occasioned between the point where the set-screw 5 bears and the lower or free end of the two portions of the thread 3. This is advantageous in the cut` ting operation, as it avoids a too heavy cut, and thus prevents the thread in the aperture from becoming broken by the action of the tap.

It will be seen that the device will work equally well if the thread is cut by advancing or turning the tap into the aperture in the ordinary manner; but I prefer to place it in the aperture as described previous to the commencement of the cut, for the reason that I am enabled to more accurately gage the cut both in amount and depth by starting it in this way. Another advantage is that iu cut ting from the bottom upward the chips or cnttings are thrown outward by the action of the tap.

I claim as my invention- In a device of the class described, the combination, with the shank 2, the lower portion of which is formed in two halves, the upper portion suitably secured together, of the threads 3, cut upon the lower or free ends of the said shank, and the set-screw 5, passing through one part of the shank and bearing upon the other ata point above the threads3 and operating to force the two halves apart, in the manner substantially as described.

In testimony whereofI have hereunto set my hand this 23d day of June, 1888.

HENRIK KELSTAD.

In presence of- R. H. SANFORD, C. L. NACHTRIEE.

ICO 

